Preheat your oven to 180°C (350°F) and prepare a 9-inch round cake pan by greasing with butter and lining the bottom with parchment paper.

In a large mixing bowl, combine room temperature butter and caster sugar, then beat until light and fluffy (about 3-4 minutes).

Add the eggs one at a time to the butter-sugar mixture, mixing well after each addition.

Sift in the self-raising flour and custard powder, then gradually combine with the wet mixture while slowly pouring in the milk until smooth.

Pour the batter into the prepared cake pan and smooth the top.

Bake for 30-40 minutes or until a toothpick inserted in the center comes out clean.

Once baked, let the cake cool in the pan for 10 minutes before flipping onto a wire rack to cool completely.